Method and apparatus for the extrusion of metal tubes and billets by an initial impulsive force and the subsequent application of uniform extrusion forces



3,397,562 L TUBES AND 2 Sheets-Sheet 1 llVVE/VTUR E J. FUCHS, JR.

ATTORNEY FUCHS, JR

/Q/QW Aug. 20, 1968 J.

METHOD AND APPARATUS FOR THE EXTRUSION OF META BILLETS BY AN INITIAL IMPULSIVE FORCE AND THE SUBSEQUENT APPLICATION OF UNIFORM EXTRUSION FORC Filed April 8, 1966 20. 1968 F. J. FUCHS, JR 3,397,562

METHOD AND APPARATUS FOR THE EXTRUSION OF METAL TUBES AND BILL-ETS BY AN INITIAL IMPULSIVE FORCE AND THE SUBSEQUENT APPLICATION OF UNIFORM EXTRUSION FORCES Filed April 8, 1966 2 Sheets-Sheet 2 lll/llllllllll lln 28 P i 56 30 j United States Patent O 3,397,562 METHOD AND APPARATUS FOR THE EXTRUSION OF METAL TUBES AND BILLETS BY AN INITIAL IMPULSIVE FORCE AND THE SUBSEQUENT AP- PLICATION OF UNIFORM EXTRUSION FORCES Francis J. Fuchs, Jr., Princeton Junction, N.J., assignor to Western Electric Company, Incorporated, New York, N.Y., a corporation of New York Filed Apr. 8, 1966, Ser. No. 541,323 16 Claims. (Cl. 7254) This invention relates to a method and apparatus for the extrusion of metal tubes and billets by an initial impulsive force and the subsequent application of uniform extrusion forces, and more particularly, to an apparatus that utilizes an impulsive type force to overcome the static friction of a tubular blank or billet against the walls of a die opening after which a hollow pressure equalizing punch maintains a constant force against the tube or billet to uniformly extrude the tubular blank or billet through the die opening.

In many ultrahigh pressure fluid forming processes, a relatively high starting pressure is required. The high starting pressure may be achieved by creating impulsive type forces in the forming chamber. In the past, explosives have been used to drive a fluid against the metal to be formed thereafter drawing the metal against a die. However, the use of explosives in such operations is relatively expensive and may represent a safety hazard.

Another type of apparatus creates the high starting forces in the forming chamber by discharging capacitors to produce a gaseous medium in the chamber. The gaseous medium often causes undesirable effects on the hydraulic properties of the forming fluid. There is still a need for metal forming apparatus having a safe, controllable system for creating a high starting pressure and to thereafter maintain a constant pressure against the end of a tube blank or billet for extruding or flanging the blank or billet.

It is an object of this invention to provide a new and improved method and apparatus for the extrusion of metal tubes and solid billets by an initial impulsive force and subsequent application of uniform extrusion forces.

It is a further object of this invention to provide an apparatus for initially imparting a high force to a forming member and then maintaining a substantially constant force against the forming member to form or extrude a tubular blank or billet.

It is an additional object of this invention to provide a method and apparatus for subjecting a static, hollow punch engaging a billet or tubular blank to a high energy impact force to initiate an extrusion of the tubular blank whereafter a constant pressure differential is maintained between the interior and exterior of the hollow punch while a substantially constant force is impressed against the tubular blank to complete the extrusion.

It is another object of this invention to provide an apparatus for increasing the pressure in a fluid medium to rupture a member to apply an impact pressure and to overcome the static friction of a tubular blank against an extrusion die and thereafter maintain a substantially constant force against a hollow punch to extrude the tubular blank at a uniform rate.

With these and other objects in view, the present invention contemplates a method and apparatus utilizing an impulsive force resulting from the hydraulic shearing of a rupturable member to impart a high impact pressure against a metal billet or tubular blank to initiate a formin operation whereafter a substantially constant force is maintained on an end of a billet to continue the forming operation at a substantially uniform rate.

More particularly, a first ram is advanced to press a first fluid against a metal disc which is only partially supported. When the pressure against the disc reaches a suflicient magnitude, the unsupported portion of the disc is sheared to apply the high pressure first fluid against a ram-mandrel with a high force of short duration to initiate an impulsive movement of the ram-mandrel. The movement of the ram-mandrel imparts a pressure buildup in a second fluid inside a hollow punch concentrically mounted on the mandrel and moves the punch against a metal billet, positioned within a die cavity, to overcome the static friction between the billet and a die orifice and impulsively move the billet through the orifice. The punch moves along the mandrel away from the ram, thereupon reducing the fluid pressure within the punch and diminishing the speed of the billet through the orifice.

As the ram-mandrel is further advanced by the first fluid, the pressure inside the punch increases and expands a resilient upper wall of the punch to permit some of the high pressure second fluid to escape to the die cavity. The pressure inside the punch will always be at a higher pressure than that in the die cavity and the periodic escape of part of the second fluid simultaneously maintains a constant pressure differential between the interior and exterior of the punch so that a substantially constant axial force is exerted on the billet by the punch during the remainder of the extrusion. This reduces the need for a high pressure fluid within the die cavity and in addition permits of a greater control of the speed of extrusion of the billet.

Other objects and advantages of the present invention will become apparent by reference to the following detailed description and accompanying drawings wherein:

FIG. 1 is an elevational view partially in section of an ultrahigh pressure forming apparatus for extruding a tubular blank in accordance with the principles of the present invention; and

FIG. 2 is an elevational view partially in section which shows the forming apparatus of the present invention adapted to extrude a solid metal billet through an extrusion die orifice.

Referring now to FIG. 1, there is shown a tubular blank 10 positioned within an apparatus that may be used to carry out the method of the present invention to form, flange or extrude the blank.

in a casing 23. The die block 21 has a die orifice 24 formed in one end thereof with the orifice extending past a beveled side wall 25 to a die cavity wall 26. In order to initially place the tubular blank 10 in the die cavity, the top of the die block 21 is formed with a threaded cavity 27 in which is secured a removable support block 28 having a threaded end 29. The block 28 has a stepped bore 30 in the lower end of which is slidably mounted a ram 31.

One end of the ram 31 is attached to a mandrel 32 which extends toward the die orifice 24 and on which may be mounted the tubular blank 10. The diameter of the mandrel 32 is less than that of the die orifice to permit the mandrel and blank to pass through the orifice during the extrusion.

A hollow forming member or punch 41 has a rigid, thick end 42 slidably mounted on the mandrel 32 and a resilient, thin, side wall 43. The side Wall 43 terminates in an annular lip 44 which is concentrically disposed about the ram 31. The rigid end 42 of the punch supports the tubular blank 10 against the die orifice 24. A fluid 45 is contained within the die cavity 26 and within an annular enclosed space 46 in the punch 41. The opposite end of the ram 31 is integral with a reduced diameter plunger 47 and forms a shoulder 48 therewith.

The plunger 47 is journalled through a small diameter portion 51 of the stepped bore 30 in top of the support block 28. The stepped bore 30 is formed with an enlarged center portion 53 for receiving the other end of the ram '31. The diameter of the support block 28 is less than that of the chamber 22. Furthermore, the block 28 has a plurality of radially extending passageways 54 to permit free flow of fluid 56 from the space between the outside of the block and the casing 23 into the center portion 53 of the bore 30 to surround the ram 31 and plunger 47.

In order to provide for the build-ups and subsequent release of an impact pressure, a severable thin metal disc or plate 61 is supported against the top of the block 28 with the plunger 47 extending therethrough. The plate may be circular in shape, but it is contemplated that other shapes will be used to correspond with the shapes of the chamber 22. The peripheral edge 62 of the disc is upturned and firmly abuts the casing 23 to form a seal between the disc and the casing. A narrow annular area of the disc, including the upturned edge, overhangs the block 28 and is unsupported therealong.

A piston 71 is concentrically disposed about the plunger 47 and is slidably mounted within the chamber 22 of the casing 23. The piston 71 extends into a high pressure fluid cylinder 72. Additional fluid 56 confined be tween the disc 61 and the piston 71 within the chamber 22 will be compressed by the piston to generate a high impact pressure.

In preparation for using the forming apparatus and practicing the method, the ram 71 is Withdrawn from the chamber 22 and the apparatus shown in FIG. 1 is disassembled so that only the die block 21 is within the chamber 22. A tubular blank is then placed on the mandrel 32 with one end abutting the end 42 of the punch 41. The mandrel and punch are inserted into the die cavity 26 until the other end of the blank contacts the beveled side wall of the orifice 24.

Fluid 45 is then introduced into the enclosed space 46 within the punch 41 after which the ram 31, with plunger 47 attached, is lowered into the punch. Additional fluid 45 is placed within the die cavity 26 to surround the punch and tubular blank 10. The block 28 is slipped over the plunger 47 and ram 31 and is turned into the threaded opening 27 in the top of the die block. At this time upper portion of the ram 31 is enclosed within the counterbore 53.

The fluid 56 is then admitted into the annular space between the support block 28 and the casing 23 whereupon the fluid flows by gravity through passageways 54 in the support block into the center portion 53 of the stepped bore 30. When the fluid 56 rises to the top of the support block, the supply is cut off and a disc 61 is placed over plunger 47 and pressed against the top of the support block. Additional fluid 56 is then piped into the chamber 22 above the disc 61.

In order to generate a high pressure against the disc 10, the piston 71 is advanced by fluid cylinder 72 to compress the fluid 56 between the disc and the piston. When the pressure within the fluid exceeds the shearing strength of the metal disc, the upturned edge 62 of the disc 61 will rupture along an edge of the support block 28 and fall into the space between the support block and the chamber 22.

The rupturing of the disc 62 impacts the fluid 56 above the disc against the fl-uid 56 between the support block and the casing. The resultant instantaneous increase in pressure is transmitted by the fluid 56 through the passageways 54 into the center portion 53 and against the annular shoulder 48 of the ram 31.

The sudden surge of energy applied to the ram 31 impulsively forces the ram 31 and mandrel 32 downwardly and slidably moves the lower end of the ram within the hollow punch 41. The fluid 45 within the enclosed annular space 46 is, in turn, compressed and thereupon exerts a force against an inner ring-like ledge 73 to force 4 the rigid end 42 of the punch downward against the top of the blank 10.

The punch 41 moves downwardly against the top end of the tubular blank 10 and forces the other end of the blank along the beveled walls 25 of the die 31 to overcome the static friction and impulsively forces the end of the blank into the die orifice 24 to initiate the extrusion of the blank.

Once the movement of the blank through the orifice has been impulsively initiated, the speed of the extrusion is reduced to a uniform rate. This may be accomplished by the punch 41 moving downwardly along the mandrel 32 and ram 31 to increase the space 46 thereupon reducing the pressure of the fluid contained therein. The pressure of the fluid against the ledge 73 is diminished and the speed of the blank through the die orifice approaches the predetermined uniform rate.

With the continued advance of the piston 71 subsequent to the shearing of the metal disc 61, the fluid 56 is thereupon subjected to a constant pressure which in turn is applied to the ram 31 to further move the ram against the mandrel 32. At the same time, the ram 31 continues to compress the fluid 45 within the hollow punch 41 to maintain a downward force against the tubular blank 10 to further extrude the blank.

During the extrusion following the initial impact, the ram 31 may move into the punch 41 at a faster rate than the punch is extruding the blank 10. This may be due to nonhomogeneous material in the blank or varying degrees of friction between the blank and the die orifice or perhaps to an irregular fit between the blank and the mandrel.

Any deviation from the uniform rate of extrusion will result in a build-up in pressure in the fluid trapped within the enclosed space 46 inside of the punch. If the pressure within the punch increases beyond a predetermined value, calculated with respect to the resilient properties of the punch material, the punch will expand and the resilient side wall 43 will move away from the ram 31 to release fluid from therewithin to the die cavity 26. The release of the excessively pressurized fluid from within the punch insures that a constant pressure differential is maintained between the interior and the exterior of the punch. The punch 41 continues to function in a normal fashion with the application of a substantially constant axial force to the blank 10 to obtain a substantially uniform rate of extrusion. The application of the axial force to the blank reduces the need for a high pressure fluid 45 within the die cavity, and, in addition, permits of a greater control of the speed of the extrusion.

In a second embodiment (see FIG. 2), the method and apparatus of the present invention may be used to extrude a billet through the die orifice 24. As shown in FIG. 2, the mandrel 32 and plunger 47 are deleted, but otherwise the apparatus is substantially unchanged. The elimination of the plunger 47 increases the area of the ram 31 which is subjected to the impulsive force of the fluid 56 thereupon resulting in a larger force which may be applied through the ram to the punch to extrude a solid billet. The billet 100 is interposed between the punch 41 and the die orifice 24 and the steps of the method as hereinbefore described are taken to extrude the billet.

More particularly, the advance of the ram 31 within the punch 41 applies forces through trapped fluid to advance the punch 41 and extrude the billet through the orifice 24. Any excessive build-ups of pressures within the punch is accompanied by a separation of the inner wall of the punch from the ram, thereby permitting the escaped fluid and reduction of pressure to insure the uniform extrusion of the billet.

It is to be understood that the above-identified embodiments are simply illustrative of the principles of the invention and numerous other modifications may be devised without departing from the spirit and scope of the invention.

What is claimed is:

1. A method of utilizing a first fluid contained behind a rupturable plate to pressurize a second fluid to exert a force against a metal billet to ext-rude the billet comprising the steps of:

increasing the pressure on the first fluid to rupture the plate and apply an impulsive force to the second fluid to initiate passage of the billet through an orifice;

further pressurizing the first fluid to apply a substantially constant force to the second fluid and said billet; and

relieving the pressure in the second fluid upon increases above a predetermined value to maintain a substantially uniform force on the billet during the extrusion thereoi.

2. A method of high initial impact forming of a tubular blank mounted on a mandrel and having one end against a die orifice comprising the steps of:

applying a pressurized first fluid to rupture a disc and generate an impulsive force;

spontaneously transmitting said force to pressurize a second fluid to initiate passage of the mandrel through the die orifice and extrusion of the tubular blank through said orifice;

continuing to pressurize said first fluid to maintain a force against said second fluid; and

relieving the pressure in the second fluid to maintain a substantially uniform force on the blank during the extrusion thereof.

3. A method of high initial impact forming of a tubular blank mounted against a die orifice comprising the steps of:

mounting the tubular blank on a mandrel of a size that will pass through said die orifice;

positioning the tubular blank and mandrel over said supporting the central portion of a rupturable disc within a fluid filled chamber; increasing the pressure of the fluid in the chamber to rupture the disc and apply an impact force to said mandrel and tubular blank to initiate passage of the mandrel through the die orifice and extrusion of the tubular blank through said orifice;

continuing the application of a force to pressurize the fluid to apply a continued force to said blank and mandrel to extrude the blank through the orifice while the mandrel passes through said orifice; and

relieving the force applied to the blank and mandrel upon increases above a predetermined value to maintain a substantially constant axial force on the tubular blank during subsequent extrusion thereof. 4. A method of high initial impact extrusion of a metal billet comprising the steps of:

placing the billet between a die orifice and an expandable fluid filled forming member which releases the fluid upon expansion of said forming member;

partially supporting a rupturable diaphragm to divide a fluid filled chamber into a first and a second section;

impressing a force against the fluid in the first section to rupture the diaphragm and impart a force to the fluid in the second section; transmitting the impact force in said second section through the fluid filled forming member to initiate passage of the billet through the die orifice; and

further pressurizing said fluid in said first section to continuously apply a force to said fluid in said forming member until such forming member expands to release said fluid to decrease the pressure Within said forming member to maintain a substantially constant axial force by the forming member on the billet during the extrusion thereof.

5. A method of high initial impact forming of a billet mounted against a die orifice in a fluid filled cavity in a die block, comprising the steps of:

forming a disc with an upturned rim having a predetermined diameter;

supporting the central portion of the rupturable disc to partition a fluid filled chamber into a first section and a second section, said fluid filled chamber being selected to have a diameter less than said predetermined diameter so that said upturned rim seals said disc against said chamber; increasing the pressure of the fluid in said first section to rupture the disc and apply an impact force to the fluid in said second section; transmitting said impact force to the billet to initiate extrusion of the billet through the die orifice; continuing the application of pressure to the fluid in said first section to apply an extrusion force to said billet; and relieving the extrusion force upon increases above a predetermined value to maintain a substantially uniform rate of extrusion.

6. A method of high initial impact extruding in a chamber having an extrusion die orifice;

mounting a tubular blank on a mandrel of a size that will pass through the die orifice;

positioning the tubular blank and mandrel between the die orifice and a fluid filled forming member;

partially supporting a rupturable disc to divide a fluid filled chamber into two sections;

increasing the pressure of the fluid in the first section to rupture the disc and release an impact force;

transmitting said impact force through the fluid in the second section to the fluid filled forming member to initiate passage of the mandrel through the die orifice and extrusion of the tubular blank through said orifice;

continuing the pressurization of said fluid in said first section to continuously apply a force against said forming member; and

releasing said fluid in said forming member upon in creases in pressure above a predetermined value to maintain a substantially uniform rate of extrusion.

7. In a high pressure extrusion apparatus for forcing a hollow billet through a die orifice;

a mandrel for supporting a hollow billet with one end abutting said die orifice;

a ram having one end abutting said mandrel;

a chamber surrounding the opposite end of said ram for receiving a fluid;

a rupturable member partially supported to extend across said chamber and said opposite end of said ram;

means for pres'surizing the fluid in the chamber to rupture said rupturable member and apply an impact force to said ram; and w a sleeve filled with fluid positioned about said ram and having one end abutting said billet for transmitting said impact force to initiate extrusion of said billet.

8. In a high pressure extrusion apparatus as defined in claim 7 wherein:

said sleeve is constructed of a resilient metal which expands away from said ram to limit the pressure build-up in the fluid within the sleeve.

9. In a high pressure apparatus for forming a tubular blank positioned within a fluid filled cavity through a die orifice comprising:

punch against said blank to initiate passage of the blank through the orifice; and

means on said punch for reducing the pressure in said punch to exert a substantially constant axial force by the punch on the blank to maintain a uniform rate of extrusion.

10. An ultrahigh pressure apparatus for extruding a tubular blank comprising:

a die block having a die orifice a one end and a bore formed therethrough at the other end with a die cavity disposed between said orifice and said bore;

a mandrel within said die cavity for supporting the tubular blank with one end abutting the die orifice;

a ram slidably positioned within said bore in said die block and having one end abutting said mandrel;

a fluid filled hollow punch slidably mounted on the mandrel with one end abutting said tubular blank, said punch having a side Wall concentrically disposed about the ram;

a supporting member secured to said die block, said member having a cavity formed therein for receiving the other end of said ram;

a fluid filled casing concentrically disposed about said die block and said supporting member, said casing spaced from said supporting member;

a metal disc positioned against and overhanging said supporting member to engage said casing and divide said casing into a first section and a second section; and

means for compressing the fluid within said first section to rupture the overhanging part of the disc and transmit an impulsively released force through the fluid in the second section into the cavity in the supporting member to impart a force to the ram to move the ram against the fluid in the hollow punch whereupon said punch is advanced against the blank to extrude the blank.

11. In a high pressure extrusion apparatus as defined in claim 10 wherein:

said side wall is constructed of a resilient material which expands away from said ram to limit the pressure build-ups in the fluid within the punch upon continued movement of the ram.

12. In a high pressure apparatus for extruding a billet positioned within a fluid fllled die cavity through an orifice at one end of said die cavity;

a fluid filled chamber;

a rupturable member extending across the chamber and the opposite end of said ram;

means for partially supporting said member to separate the chamber into a first section and a second section;

means for pressurizing the fluid in said first section to rupture said partially supported member and impart a high energy short duration force through the fluid in said second section to said ram to move the ram against the fluid in the punch whereupon the punch extrudes the billet, and for thereafter imparting a generally constant force to said fluid;

a fluid filled hollow punch in said die cavity having one end abutting said billet to support the billet against the orifice;

a ram having one end extending into said second section of said fluid filled chamber and the other end slidably extending into said hollow punch to transmit said short duration force to the fluid in the punch and move the punch against the billet to overcome the static friction of the billet against the orifice whereupon the punch slidably moves along the ram to reduce the fluid pressure within the punch;

means on said hollow punch rendered elfective upon increases above a predetermined value for releasing fluid from said hollow punch to said die cavity to limit the pressure build-up within the punch and exert a constant force of the punch against the billet to maintain a uniform rate of extrusion. 13. In a high pressure extrusion apparatus for forcing a tubular blank positioned within a die cavity in a die block through an orifice;

a slidably movable ram extending from within said die cavity through said die block;

a mandrel within said die cavity extending from said ram for supporting the tubular blank with one end of the blank abutting the die orifice;

means responsive to movement of said ram for advancing said blank through said die orifice to extrude said blank;

21 support block secured to said die block, said support 'block formed with a cavity for receiving said ram, said support block also having a plurality of radial passageways extending from the cavity to the exterior of said block and a bore extending axially from the cavity to the top surface of said block;

a casing concentrically disposed about and spaced from said support block, said casing having a chamber containing a fluid which surrounds said support block and fills said cavity;

a rupturable member partially supported on said support block to extend across said chamber;

a plunger extending from the ram within said cavity through said bore in said support block and said rupturable member, said plunger forming an annular shoulder area with said ram; and

means for pressurizing the fluid in the chamber to rupture said rupturable member and apply an impact force through said fluid in said passageways to said shoulder area of said ram.

14. In a high pressure apparatus for extruding a billet positioned within a die cavity in a die block through an orifice at one end of said die block;

a support block secured into the other end of said die block, said support block having a cavity formed therein with a plurality of passageways extending radially from said cavity to the exterior of said block;

a fluid filled chamber concentrically disposed about and spaced from said support block, said fluid surrounding said block and filling said cavity;

a disc shaped diaphragm positioned against said support block to partition the chamber into a first section and a second section, said diaphragm having an upturned edge overhanging said support block with a corner of said edge engaging said chamber to seal said first section from said second section;

a ram extending from within said cavity in the support block through said die block into said die cavity;

means for compressing said fluid within said first section against said diaphragm to further press said corner of said edge into said chamber until the yield strength of the diaphragm is exceeded whereupon the upturned edge is sheared off and an impulsive force is imparted through said fluid in said second section and said passageways to the ram in said cavity; and

means responsive to the force against said ram for advancing the billet through the orifice to extrude the billet.

15 The method of extruding a billet, comprising the steps of:

applying said force suddenly to said billet to overcome said friction and to initiate extrusion of said billet through said die, and

thereafter, controlling said force applied to said billet at a substantially constant level suflicient to continue to extrude said billet through said die.

9 10 16. The method of extruding a billet, comprising the References Cited steps f f 1 m t1 UNITED STATES PATENTS genera mg a orce rom a slnge source su cien y great to both extrude said billet through a die and iggg to overcome static friction between said billet and 5 1903475 4/1933 Rhodeg 2,164,640 7/1939 Cannon. applymg said force suddenly to said blilfii to overcome 3,057,313 10/1962 setsgn said friction and to initiate extrusion of said 'billet 3,090,113 5 19 3 Karpovich through said die, and 3,181,328 5/1965 Zeitlin 7256 subsequently, controlling said force applied to said 10 billet at a level suflicient to continue to extrude said CHARLES LANHAM Pnmm? Examine"- billet through said die. K. C. DECKER, Assistant Examiner. 

15. THE METHOD OF EXTRUDING A BILLET, COMPRISING THE STEPS OF: GENERATING A FORCE FROM A SINGLE SOURCE SUFFICIENTLY GREAT TO BOTH EXTRUDE SAID BILLET THROUGH A DIE AND TO OVERCOME STATIC FRICTION BETWEEN SAID BILLET AND SAID DIE, APPLYING SAID FORCE SUDDENLY TO SAID BILLET TO OVERCOME SAID FRICTION AND TO INITIATE EXTRUSION OF SAID BILLET THROUGH SAID DIE, AND THEREAFTER, CONTROLLING SAID FORCE APPLIED TO SAID BILLET AT A SUBSTANTIALLY CONSTANT LEVEL SUFFICIENT TO CONTINUE TO EXTRUDE SAID BILLET THROUGH SAID DIE. 